The present invention relates to a method for detecting vertical gusts of wind on board an aircraft in cruising flight and to a detection device employing said method and the application of both to the control of said aircraft. The vertical gusts of wind to which the present invention relates are swirling turbulence (rather than high-frequency turbulence that causes vibration), generated by swirling rollers of the vortex type, which subject the aircraft passing through or close to them to an upward (or downward) gust of wind then to a downward (or upward) gust of wind that lasts for a few seconds, or alternatively, to a succession of upward and downward gusts of wind if there are a number of vortices.
If the aircraft is on manual control in the cruising flight and encounters an upward gust of wind of this kind, it is subjected, first of all, to a high positive load factor which means that the pilot reacts with a nose-down command on the aircraft, in order to counter the upward wind effect. However, the gust then changes direction and the wind becomes a downward gust, which means that the pilot's nose-down action is now adding to the downward gust of wind to apply a negative load factor on the aircraft, which load factor is even higher than the load factor that would be the result of the gust itself. This may then cause injury to passengers and damage to the aircraft.
The same thing happens if the aircraft has an automatic pilot and if this automatic pilot is engaged during the cruising flight at the time when the upward gust of wind is encountered.
What happens is that this gust of wind causes the automatic pilot to disengage and a switch to manual control, either automatically by the action of protection devices (for example angle of incidence protection) or through an instinctive action by the pilot on the stick. There too, the pilot's nose-down action will add to the reverse gust of wind.
Of course, what was applied hereinabove is applicable mutatis mutandis to instances where a gust of wind which starts out downward then switches upward is encountered.
Thus, from the foregoing, it will be readily understood that in general, any control action to counter a gust of wind produces its effect at the moment said gust changes direction, which means that this control action unfavorably increases the already high load factor to which said gust is subjecting the aircraft.